Immunologic response in pregnancy. Its role in endocrine disorders of pregnancy and influence on the course of maternal autoimmune diseases.

During gestation, the immune system is challenged with establishing tolerance to the partial allograft represented by the paternal contribution to the fetal genome. That fact that cell-mediated immunity is decreased while T-cell-dependent immunoglobin production remains intact or is increased is generally accepted. This latter phenomenon can be placed in teleological perspective in terms of providing passive immunity to the fetus. T-cell lineages that diverge based on function and cytokine production have been identified. Pregnancy is associated with a relative increase in Th2-associated immunity, characterized by increased production of the cytokines IL-4 and IL-10. These changes occur concomitantly with increased immunoglobulin production and decreased Th1 immunity. IL-2 and interferon secretion characterize Th1 immunity, facilitating allograft rejection. These changes in Th1 and Th2 have implications for the clinical course of a several autoimmune diseases that may complicate pregnancy and the postpartum period.